Maintenance of program transmission circuits



Nov. 9, 1937. H. A. AFFEL 2,098,329

MAINTENANCE OF PROGRAM TRANSMISSION CIRCUITS Filed Sept. 24, 1935 /7 70 6 V we flgdiblei'a igrzal load Speaker 07' Receiver Terminal Frog/um Repeater lle aenzter Franz V fi j Central R f L Circuit t .7V0i-Se orXTzZ/c 62 97402. W. 5 I I Opel (Lime Szgmzl I I R; I I

12 III INVENTOR ATTORNEY Patented Nov. 9, 1937 PATENT OFFICE MAINTENANCE OF PROGRAM TRANSMIS- SION CIRCUITS Herman Andrew Afiel, Ridgewood, N. J., assignor to American Telephone and Telegraph Company, a corporation of New York Application September 24, 1935, Serial No. 41,920

13 Claims.

This invention relates to improvements in maintenance of program circuits of the type used in transmitting to various points programs such as are broadcast by radio or otherwise. More specifically, this invention relates to a method and means for monitoring and locating troubles on these program circuits. The requirements on program transmission, as T to quality, continuity of service, freedom from extraordinary noise and freedom from crosstalk, are very severe and considerable efiort is spent in measuring and monitoring these circuits. Usually it calls for a more or less continuous listening and monitoring at key points when the circuits are in v wuss; The purpose of this invention is to reduce or tain circuit arrangements which, in the event of abnormal conditions calling for rectification, will automatically give a signal calling attention to the abnormal condition.

"The invention'will be better understood by reference to the following specification and accomf panying drawing, in which Figure 1 shows asimple circuit arrangement carrying out the purposes it of my invention; Fig. 2 is a modification of the circuit of Fig. 1; Fig, 3 is a different type of circuit providing signal operation at a plurality of points,

' and Fig. 4 is still a further modification'applicable'to two program circuits in parallel.

' Referring more specifically to Fig. 1, there is 1 shown a monitoring arrangement which may be attached to a program circuit L by being bridged thereon. In this case monitoring is carried on with an attendant listening to a loudspeaker LS, and this may be under conditions in which the room noise is excessive. Part of the monitoring function consistsin noting whether the program isfbeing reproduced properlyin the loud speaker, but another important part consists in noting the transmission conditions of the program circuit during periods of program silence, havingin mind,

arly, such things as the amount of noise Qpre'sent on the line. Under the conditions which i exist in actual operation there may be other monitoring loud speakers giving. out sound in the vi- ,cinity of the loud speaker in question. While 50 there is no great difiiculty in listening to the cir- .cuit 'jduring periods when the program is being tra nsmitted'it may be difficult to listen for noise or crosstalk during the quiet intervals in the prograin. To overcome this effect I arrange in the 55 taunt of Fig. [for a supplemental visible or audisound signals coming over the program circuit through an amplifier or equivalent device bridged across the program circuit. When program is coming in the relay 1 is operated and opens the circuit of the signal device 9. During periods of program silence, however, the relay! isreleased,"

closing the circuit through amplifier ID to the signaling device 9. This latter can be adjusted to an appropriate sensitivity to give an alarm or other indication if noise or crosstalk. on the program circuit is in excess of a predetermined amount.

A modification of this circuit is shown in Fig. 2 in which the loud speaker is, itself, the signal or alarm device. In this figure'an' attenuating device, shown here as a resistance element I2, is"

bridged across the input of the loud speaker. During periods of incoming program the amplifier-detector 6 operates the relay l to place the resistance i2 as a shunt across the loud speaker terminals, thus lowering'the gain of the circuit,

this gain, under these conditions, being such as to give volume of the desired amount in the loud speaker. During periods of program silence, however, the shunt I2 is removed and the gain for the loud speaker is accordingly stepped up very substantially to make it highly responsive to noise or crosstalk on the line, thus enabling it to override the room noise. It is to be understood that there may be a plurality of points'on'the circuit supplied with the devices of Fig. 1 and Fig. 2.

Fig. 3 shows a further modification of my invention. In this case a plurality of stations A, B, and C at key points of the program circuit are shown, an-din parallel to the program circuit there is provideda low grade signaling circuit such as a telegraph circuit which is to be used as a signaling or control circuit. Specifically, there is bridged across the program circuit at the sending end (station A) an amplifier-detector circuit 20. A relay R from the output of this amplifier-detector circuit sends a signal down the control circuit to stations B and C which signal ispicked up by other relays at the various key points. In the particular circuit here shown there is a similar amplifier-detector 2 I, etc., at each monitoring point, these amplifier-detectors controlling relays R1, R2, etc. Also, at each of these stations there is a relay, referred to above, controlled by the low grade control circuit, these relays being indicated as R1, R2, etc. At any one monitoring station the relays such as R1 and R1 are interlocked as shown, with secondary signal circuits which may consist of lamps or audible signals, as preferred. I

If now speech is applied to the sending end of the program circuit it operates the relay .R, thus applying battery to the control circuit which in turn will operate the relays :R1'., R2, etc.,,but this same program arriving at the monitoring points of stations B, C, etc., will operate the relays R1, R2, etc., and thus nothing happens to the secondary signal indicators S1 or .82. If, however, during a pause in the program speech or music, relay R, is released, thus releasing relay R1, and if at the same time noise -or crosstalk has entered the program circuit in the first section of the line sufiicien't to operate Ethe .amplifier-detector and :pull .up the relay R1, :then a signal will be given on '81. on :the other hand, if the line noise and crosstalk conditions are setisfactory this signal will not be actuated.

Signal S2 will be operated :in case program is operating the control circuit through relay R, and this speech does not appear atthe monitoring point to operate relay B1. In this 'caserelay R1 is released thus completing the-circuit to sig nal S2 and giving an indicationof an open line at a point somewhere between the transmitting station and "the monitoring point at which the indication is made.

It will be noted that :this ,figure illustrates the use of a:D.JC.. circuitas the control channel. 0b viously, many variations may be made in this regard. :Such a control channel, for example,

mightb'e a carrier circuit or even one of the multiple circuits of a rapid-acting distributor which could be used to distribute signals for several paralleling program controls. .Again :it is evident that the signals at :the repeater may be relayed to 'a central point such as the receiving terminal. Also, the control circuit may .be .operated either open circuit or closed circuit. .If operated as a closed circuit, as shown, it should preferably be carried over a different pair :of wires from the program circuit.

Fig. 4 is an arrangement .hav-ing general teatures analogous to that of 3, but is particularly applicable in the 'case of two paralleling program 'circuits transmitting the two channels of an acoustical perspective system. In this arany event, i.t.is expected that the two relays would be operated-and released substantially simultaneously when the-circuits are in proper condition. If, however, a break should occur in circuit l duringa period of music transmission, relay R1 would be released and relay R2 drawn up, thus completing the circuit through the secondary relayRs which then would-operatethe alarm circuit. Relay R3 should preferably be somewhat sluggish in operation because of slight diflerences in synchronism in the operation of relays R1 and R2.

Similarly, if during a quiet interval in the music, circuit I should pick up noise suflicient to 5 pull up the armature of relay R1 the relay R2 would be unaffected and an alarm signal would also be transmitted. Otcourse, if both the paralleling circuits are similarly affected by noise, or if they both sufier an interruption simultane- 10 ously, no alarm would be given, but the chance of :this occurring is .not large. Furthermore, it is'to be understood that at such a. listening point there would ordinarily be a loud speaker bridged across at least one of the lines. 5 Obviously many variations may be introduced without departing from the spirit of this invention. For example, the low grade control circuit of Fig. 3 could be used in connection with the two parallel, program circuits of Fig. 4. Also, it is evident that in the event'of aplurality of monitoring points, such as contemplated :in connection with Figs. 3 and 4,the signalsorra-larms (may be confined to these -monitoring points-'01 may be transmitted by any suitable signalingrgs channels to some central point for a general supervision. Or, again, *arm-unciator arrangements might be provided at each (monitoring point which would receive signals irom each 01 the other monitoring .points all directed to them end of carrying out the purposesof this invention, as previously stated. a

What is claimed is: a I

.1. In a program transmission line,-,-mean s ,ipr monitoring the line comprising .a signal respon-ans sive device bridged across the lineand responsive to line signals, asecondarycircuitand .an

electrically operated relay .socontrolled :by we nals, an amplifier-detector bridged across the transmission circuit, anda relay controlled'thereby adapted to remove the shunt wheninoprogranr is present to render the loud speaker more sensi-"-" ti-ve .to circuit disturbances.

4. In a program transmission linesystem, an amplifier-detectorbridged across thejline at each I of .a plurality of .points, and secondary circuitg controlled by .each of .said amplifier-detectors lto give a signal .dur'ing'periods ofprogramsilence to indicate abnormal conditions on 'the'line.

5. Ina transmission line system, an amplifierdetectorbridged across ltheiline at each:of.aplu-.. rality of points, and secondary circuits controlled by each of said amplifier-detectors to given signal to indicate .a break in the line or the condition of excessivenoise on the'line.

6. .In .a .program transmission .system, a .lhigh gm grade transmission circuit for program, a .relay circuitbridged across-the line. at .eachof a,.plurality of widely separatedgpoints, a vlow .grades'ignal circuit or channel parallel to .the transmission circuit, relays associated with .the second-circuit 35 at each point of a relay on the first line, and signal devices at each of said points controlled jointly by the two relays at that point to indicate abnormal conditions in the line.

7. The combination of claim 6 characterized by the fact that one of the amplifier-detector relays is near the program source and opens the second line during periods of program silence so that none of the subsequent relays on that line is operated.

8. The combination of claim 6 characterized by the fact that there are two signal devices at the said points, one of which is operated in case of a break in the transmission line and the other in case of excessive noise in the preceding section of the line.

9. In a program transmission system adapted for acoustical perspective and comprising two similar parallel transmission circuits, two relays at a monitoring point, one associated with each transmission line, and a secondary indicating circuit so controlled by the two relays that no indication is given when the program is present or absent on both lines and an indication is given when the program is absent from one line.

10. In a program transmission system adapted for acoustical perspective and comprising two similar parallel transmission circuits, two relays at a monitoring point, one associated with each 7 cation is given when the program is present or absent on both lines and gives an indication when program is absent from one line or when there is excessive noise on one of the lines.

11. In a program transmission system adapted for acoustical perspective and comprising two similar parallel transmission circuits, derived circuits from each of these transmission circuits at a monitoring point, a secondary signaling circuit at said monitoring point, the derived circuits so controlling the secondary signal circuit as to indicate substantial difference in the condition of the two transmission lines. I

12. In a program transmission line, means for monitoring the line comprising a signal responsive device associated with the line and responsive to line signals, a secondary signal circuit, and electrically operated means so controlled by said responsive device as to cause said signal circuit to be operated during periods of program silence on the transmission line.

13. In a transmission line, means for monitoring the line comprising a rectifier bridged across the line and responsive to line signals, a secondary signal circuit including a signaling element, and electrically operated means so controlled by said rectifier as to operate the signaling element at said secondary circuit during periods of program silence, to indicate presence of excessive disturbance.

HERMAN ANDREW AFFEL. 

